Laser printers and other electronic equipment need to use an electronic high-voltage DC power supply whose voltage is adjustable in a wide range, with this high-voltage DC power supply typically generated by a controlled electronic high-voltage generator. Many types of laser printers and other equipment need this multi-channel independent adjustable high-voltage DC power supply, which is usually achieved by a plurality of independently controlled electronic high-voltage generators. High-voltage transformers, high-power transistors and other large size, high cost components have to be used in the electronic high-voltage generator, and therefore the multi-channel independent adjustable high-voltage DC power supply composed of a plurality of independent high-voltage generators has the disadvantages of large volume and high cost.
Reference [1] (ZL 201210014420.6 A High-voltage Voltage Regulating Circuit) and Reference [2] (ZL 201210014640.9 A Multi-channel High-voltage Output Circuit Sharing Reference High-voltage Source) provide a technical solution of generating the multi-channel independent wide-range adjustable high-voltage DC power supply by a common high-voltage generator, which has the outstanding advantages of small size and low cost. In the technical solution of wide-range voltage regulation provided by References [1] and [2], a series voltage regulating link and a parallel voltage regulating link together compose a series-parallel voltage regulator, in which a fixed high-voltage reference source can be used to generate the wide-range adjustable high-voltage output. The multi-channel independent wide-range adjustable high-voltage output can be achieved just through a plurality of series-parallel voltage regulators and a common high-voltage generator.
However, in the technical solution of making the series voltage regulating link and the parallel voltage regulating link coordinate to achieve the high-voltage regulation as disclosed in References [1] and [2], the series voltage regulating link and the parallel voltage regulating link are both directly controlled by a controller, which has a problem that the series voltage regulating link and the parallel voltage regulating link are difficult to have their working ranges accurately adapted to each other. Ideally, the transistor in the parallel voltage regulating link should be cut off when the transistor in the series voltage regulating link is working, and the transistor in the series voltage regulating link should be cut off when the transistor in the parallel voltage regulating link is working, which should be accurately adapted to each other. Due to discreteness and a variety of bias and drift of the parameters of the electronic components, using the technical solutions disclosed in References [1] and [2] is difficult to realize the ideal and accurate adaptation of the working ranges of the series voltage regulating link and the parallel voltage regulating link. If the transistor in the series voltage regulating link and the transistor in the parallel voltage regulating link are working at the same time, which can be called working range overlap of the series voltage regulating link and the parallel voltage regulating link, a loop will be formed in the overlapping region that is invalid for voltage regulation, thereby increasing the burden of the common reference source and additional circuit loss; if the transistor in the series voltage regulating link and the transistor in the parallel voltage regulating link are cut off at the same time, which can be called a neutral region between the working ranges of the series voltage regulating link and the parallel voltage regulating link, the series voltage regulating link and the parallel voltage regulating link both lose the response to the control signal in the neutral region, which will result in a phenomenon of voltage transiently going out of control, thus causing non-smooth or non-linearity problem of the voltage regulation characteristics. In addition, the technical solutions disclosed in References [1] and [2] are only applicable to the adjustment of the single-polarity DC high voltage, and cannot meet the requirements of a lot of laser printers and other equipment for a wide-range positive-negative adjustable high-voltage DC power supply.